2013 is the 50th anniversary of the annual Black Eagle Survey in the Matobo Hills outside Bulawayo, Zimbabwe, making this the longest running survey of its kind in the world.

Our story begins with a game ranger, W. R. Thomson, who was stationed in the Rhodes Matopos National Park in 1959-60. Thomson was impressed by the number of black eagle pairs he observed whilst monitoring the area for which he was responsible. The scientific name for this bird is Aquila verreauxii - recently renamed in English as the Verreaux’s eagle.

When he left the Matobo Hills, Thomson provided his records for the use of the Department of National Parks. He had compiled a list of 37 nest sites, or eyries, of which 35 were within the Park. In 1961, Carl Vernon, a student teacher in Bulawayo, obtained Thomson’s list and set out to locate the eyries listed by Thomson, also recording the eyries of additional pairs he observed whilst checking the known pairs.

Vernon, like Thomson before him, numbered each nest, and also recorded a map reference, as well as adding references for Thomson’s nests. By the end of 1964, Vernon and Matabeleland Branch members of the (then) Rhodesian Ornithological Society, had recorded a total of 68 nest sites. In 1963 and 1964, Valerie Gargett accompanied Vernon on some of his trips into the Matopos, adding and another skilled naturalist to the tale.

At end of 1964, Vernon left Bulawayo, and in 1965, under the leadership of Gargett, the Matabeleland Branch of the Ornithological Society took responsibility for the survey. The society is now known as BirdLife Zimbabwe.

Today, the survey is still being conducted following the format and guidelines introduced by Gargett. The survey is conducted with the permission of the Parks and Wildlife Management Authority, and a research permit is obtained every year.

The survey runs from March to November annually, with volunteer teams having to submit reports by specific dates. The results of the survey are compiled and published in The Honeyguide, the journal of BirdLife Zimbabwe.

The results over the years have shown breeding success of the eagles to be variable, with unconfirmed reasons for these variations. As is the law of nature, every year when we think we may have found a reason, something else happens that sends us back to the drawing board.

It has been established that the hyrax (commonly known as the dassie) is the main prey of the black eagle. To try and anticipate the survival and continued success of the species, BirdLife Matabeleland Branch conducts an annual hyrax population census in May of each year. The same teams which monitor the eagles carry out this census.

This survey began as, and still is, a population and breeding study. It is still being carried out entirely by volunteer members of BirdLife Zimbabwe – Matabeleland Branch, and remains the longest standing continuous survey of its kind in the world.

I close with the words with which Gargett ended her book: The Black Eagle – A study (1990): “It is intended to continue the Breeding Survey for as long as circumstances and the availability of helpers permit.”